Field of the Invention
The present invention relates to vehicle headlight control devices that control light distribution of headlight.
Description of the Background Art
A vehicle headlight control device has been known which performs a so-called light distribution control by detecting, in front of a driver's (user's) vehicle, another vehicle (forward vehicle such as a preceding vehicle or an oncoming vehicle) with the use of a camera or the like, and changing a region to be illuminated by a vehicle headlight (headlamp) based on the detection result. See, for example, Japanese Laid-Open Patent Publication No. 2014-168984, Japanese Laid-Open Patent Publication No. 2012-166633, and Japanese Laid-Open Patent Publication No. 2014-168985.
Such a vehicle headlight control device controls light distribution of the headlamp so as to reduce generation of uncomfortable glare (dazzling light) by which a driver of the forward vehicle is dazzled, and simultaneously assure, for a driver, a field of view in front of the driver' vehicle during driving at night. For example, light distribution of the headlamp is controlled such that a non-illumination region (or may be referred to as a light-shaded region) which is not illuminated by light is formed around the forward vehicle detected by the camera, and an illumination region which is other than the non-illumination region and is illuminated by light, is formed.
In the vehicle headlight control device that controls the light distribution, for example, deviation in illumination axis may occur due to variation in mounting of components (such as a sensor or a headlamp), or delay in light distribution control may occur due to variation in performance between the components. Therefore, in the conventional vehicle headlight control devices, in addition to light being blocked in a range corresponding to a width of the forward vehicle, no illumination region is set immediately lateral to the forward vehicle, and the illumination regions are set so as to be spaced, from the left and right lateral ends of the forward vehicle, by a predetermined distance (hereinafter, referred to as “margin distance”) in the vehicle width direction. In the conventional vehicle headlight control devices, by the margin distance being provided, generation of uncomfortable glare on the forward vehicle due to the above-described variation is reduced. The margin distance may be represented as a margin angle.
However, in the conventional vehicle headlight control devices, the margin distances that are set from the left and the right lateral ends of the forward vehicle are constant in width regardless of a distance between the driver's vehicle and the forward vehicle. That is, both in the case of the forward vehicle being close to the driver's vehicle and in the case of the forward vehicle being distant from the driver's vehicle, the margin distances from the illumination regions to the left and the right lateral ends of the forward vehicle are the same.
In the illumination region having been thus set, as shown in FIG. 8A, a ratio (m/W1) of a margin distance m for each of the left and the right sides relative to a vehicle width W1 of a forward vehicle 201 is reduced when the forward vehicle 201 is close to the driver's vehicle. Therefore, for example, a person 202 near the forward vehicle 201 can be illuminated, whereby visibility in front of the driver's vehicle is good. However, as shown in FIG. 8B, a ratio (m/W2) of a margin distance m for each of the left and the right sides relative to a vehicle width W2 of a forward vehicle 203 is increased when the forward vehicle 203 is distant from the driver's vehicle. Accordingly, in this case, for example, a person 204 near the forward vehicle 203 is not illuminated at all or not sufficiently illuminated, whereby visibility in front of the driver's vehicle becomes worse.